Electro-hydraulic lift for human support



NOV. 23, 1965 p, C. JOHNSON 3,218,804

ELECTRO-HYDRAULIC LIFT FOR HUMAN SUPPORT FIG I PHILIP C.JOHNSON i -BYCPed/zceqzlclhbrlha@ Afornevs.

Nov. 23, 1965 P. c. JOHNSON 3,218,804

ELECTRO-HYDRAULIC LIFT FOR HUMAN SUPPORT Filed Oct. 9, 1961 4 Sheets-Sheet 2 Aorneys Nov. 23, 1965 P. c. JOHNSON ELECTRO-HYDRAULIC LIFT FOR HUMAN SUPPORT 4 Sheets-Sheet 3 Filed Oct. 9, 1961 FIG. 6.

INVENTOR. PHILIP C- JOHNSON. BYea/wef '11; ,l

FIG- 2A V /Lzo Nov. 23, 1965 P. c. loHNsoN ELECTRO-HYDRAULIC LIFT FOR HUMAN SUPPORT 4 Sheets-Sheet 4 Filed Oct. 9. 1961 NN no. wo.

Aorneys United States Patent O 3,218,894 ELECTR-HYDRAULIC HFT FR HUMAN SUPPRT Philip C. johnson, Cincinnati, Ohio, assigner to F. @i F.

Koenigkramer Company, Cincinnati, Ohio, a corporation of @hin Filed Oct. 9, 1961, Ser. No. 14.3,S69 11 Claims. (Cl. titl- 52) This invention relates to electro-hydraulic lifts for chairs, operating tables and the like and particularly to electro-hydraulic lifts which may be used to precisely vertically position a chair or operating table supported thereon, whether that position is approached from above or below.

Another object of this invention is to provide an electrohydraulic lift for chairs, operating tables and the like, such as are often used by physicians and surgeons in examining and treating patients.

Another object of this invention is to provide a single pedal controlled electro-hydraulic lift, which starts, operates and stops smoothly and quietly.

Another object of this invention is to provide a device of the above character in which manipulation of said single pedal determines the direction and speed, not in excess of the maximum, of operation of the lift.

Another object of this invention is to provide a device of the foregoing character which may be stopped precisely in any desired position of elevation, without overrunning, irrespective of the direction from which that position is approached.

A further object of this invention is to provide a device of the above character requiring only one check valve which closes to form a seal, against hydraulic liquid, which is substantially non-leaking over extended periods of time.

Another object of this invention is to provide a device of the above character in which pre-operation pressurebuild-up-time is kept to a minimum, while operation of the pump driving motor is under pedal control and limited to occasions when lift raising is desired.

Another object of this invention is to provide a device of the above character which may be completely assembled, charged With hydraulic fluid, sealed and tested in the factory before shipment for use.

Another object of this invention is to provide a device of the above character in which an acoustic lter is provided in an hydraulic system which is completely iilled with hydraulic liquid.

The above and other features and objects of this instant invention will in part be obvious and will in part be apparent to those having ordinary skill in the art to which this invention pertains, from the following description and the accompanying drawings in which:

FIG. 1 is a top plan view, partly broken away, showing an electro-hydraulic lift device embodying the instant invention, incorporated in a chair;

FIG. 2 is a fragmentary view in side elevation taken generally on the line 2-2 in FIG. 1;

FIG. 2A is a fragmentary view similar to FIG. 2 but showing additional details;

FIG. 3 is a fragmentary view in elevation, partly in section, of the device illustrated in FIG. 1;

FIG. 4 is an enlarged fragmentary view, partly in section, s-howing the cooperation of parts of the raising and lowering valve forming part of the device illustrated in the drawings, the valve being in one position;

FIG. 5 is similar to FIG. 4 and shows the valve in a different position;

FIG. 6 is similar to FIGS. 4 and 5, but shows the valve in a third position;

ice

FIG. 7 is a fragmentary view in side elevation, partly broken away, illustrating details of construction of a lift cylinder and reservoir structure forming part of the device illustrated in the drawings;

FIG. 8 is a view in horizontal section of the structure shown in FIG. 7;

FIG. 9 is a fragmentary view in vertical section taken along line 9-9 in FIG. 8;

FIG. 10 is a fragmentary view in vertical section taken along the line 10-10 in FIG. 8;

FIG. 1l is a fragmentary view in vertical section taken along the line 11--11 in FIG. 8;

FIG. 12 is a fragmentary view in side elevation of a portion of an acoustic lter forming part of the structure illustrated in FIG. l; and

FIG. 13 is a fragmentary view in horizontal section taken along the line 13-13 in FIG. 3.

In the specification and drawings like reference characters identify like parts.

The illustrative embodiment of the instant invention shown in the drawings and described hereinafter is an electro-hydraulic ylift unit adapted for use in a lift chair such as may be used by a dentist, a physician or surgeon engaged in diagnosis or treatment of afllictions of the eyes, ears, nose, throat or other portions of the human anatomy, or in other activities in which lift chairs may be utilized.

The various hydraulically lifted chairs used heretofore have shared various qualities which are undesirable. These qualities included noisy operation, jerking or bumping upon starting or stopping of the lift, overrunning of the lift past the desired stopping elevation, unsealed hydraulic systems which are less reliable and which require removal of hydraulic fluid before relocation of the chair or other device, inclusion of air bells and associated valving in unsealed hydraulic systems which require periodic servicing to mention some, but not all, of the defects.

The illustrative embodiment shown in the drawing includes chair base 20 adapted to rest upon a suitable supporting surface such as a floor, not shown.

An hydraulic lift unit 21 is secured in upright position upon chair base 20 by means of a plurality of Screw bolts 23 cooperating with integral lug portions 221 of lift unit base 22 and in threaded engagement with chair base 20. Cylindrical shell 24 encircles an upstanding boss portion 222 of unit base 22 in cooperation with annular sealing gasket or packing 25 supported in groove 251. Cylindrical shell 24 extends upwardly from hydraulic lift base 22 to sump head 26, of which a depending boss portion 262 is received in the upper portion of shell 24. Packing or seal gasket 27 is substantially received and supported within an annular groove provided in boss 262 and in sealing cooperation with shell 24. A plurality of tie bolts 28, exemplified by that shown in FIG. 3 are provided with their threaded lower end portions 29 in threaded engagement with base 22 and their upper portions extending through respective apertures provided in sump head 26, lock washer 30 and nut 31. Each of the respective nuts 31 is in threaded engagement with a threaded portion 32 of a respective tie bolt 28 such that appropriate rotation of nuts 31 serves to draw base 22 and sump head 26 axially toward each other to firmly clamp the radial end faces of shell 24 against the respective opposed radial face 34 of base 22 and radial face 35 of sump head 26.

Base 22 has a threaded axial recess adapted to receive cooperating threads 36t of cylinder 36, with its lower radial end face disposed in sealing engagement with gasket 37. Cylinder 36 extends axially upward Within shell 24 and through an axial aperture provided in sump head 26 to an upper radial end face 38 as shown in FIG. 3. Sealing ring 41 is substantially received in an annular groove provided in sump head 26 in sealing cooperation With sump head 26 and the external surface of cylinder 36. Base 22, sump head 26, shell 24, cylinder 36, sealing means 25, 27, 37 and 41 are secured in cooperating relation by tie rods 28 and nuts 31 so as to define a sump chamber 39 annularly of cylinder 36.

As shown in FIGS. 8 and 1l base member 22 supports a filter or screen 43 through which hydraulic fluid passes as it is drawn from the sump 39 through outlet passage 44, fitting 45, tube 46 and fitting 47 into pump 48. Pump 48 in the embodiment shown in FIG. l of the drawings, is secured to and driven by motor 49. Details of construction of pump 48 are not shown in the drawings, but I prefer a gear pump in which appropriate parts are lapped or honed to close tolerances for desirable efficiency. Motor 49 is equipped with a starting relay 50 and is preferably one which has a high starting torque so as to quickly reach normal operating speed and which also operates quietly with minimum vibration. When motor 49 drives pump 43 such that hydraulic fluid is discharged from pump 48 through a line comprising fitting 51, tube 52, and fitting 53 into chamber or compliance element 54. As shown, element 54 defines a chamber having substantial volume and a cross-sectional area substantially greater than the cross-sectional area of the line 51, 52, 53 delivering hydraulic fluid to it.

Hydraulic fluid is discharged from compliance element 54 through a long line of substantially smaller crosssectional area comprised of fitting 55, tube 56 and fitting 57 through the latter of which fluid is discharged from the line into a ysecond compliance element 58, similar to element 54. Hydraulic fluid is discharged from compliance element or tank S through a second long line of substantially smaller cross-sectional area than that of element or tank 58 and composed of fitting 59, tube 66, fitting 61, bore or passage 62, provided in base member 22 of the hydraulic lift unit, well 63, fitting 64, tube 65 (shown in FIGS. 9 and 10), fitting 66, spring biased check valve 66C, which permits fluid ilow from pump 48 toward passage 67, and passage 67 into valve well 69 provided in member 22. As shown in FIG. 10, passage 67 has one end closed by plug 66 and its other end is in communication with valve well 69 provided in base member 22.

As shown in FIGS. 3, 4, 5, 6, 10, and l1, compression spring 70 stands in well 69 on the bottom 71 thereof. Spring 70 supports spherical valve member 72 and urges same away from well bottom 71. Hereinafter the portion of well 69 in which spring 70 and valve ball 72 are disposed may be referred to as the ball chamber 73. As shown most clearly in FIGS. 4, 5, and 6, ball chamber portion 73 of Well 69 is of the smallest cross-sectional area. Immediately adjacent thereto and remote from well bottom 71 is an enlarged valve seat insert receiving portion of well 69 in which valve seat insert 74 is received in predetermined spaced relation to Well bottoni 71, the radial abutment face 75 serving to index valve seat 74 by precluding further advancement of the seat toward well bottom 71. Valve body 76 has a threaded shoulder 77 in cooperating engagement with complementary threads provided in the wall yof well 69 adjacent the mouth of the well. Flange 78 of the valve body is adapted to engage base member 22 annularly of the mouth of valve well 69 and thereby limit advancement of the Valve body 76 into well 69. The portion of valve body 76 extending from shoulder flange 7S toward valve seat 74 is preferably of such length as will result in engagement of radial end face 79 of the valve body, With the opposed radial end face 80 of valve seat insert 74. Thus, valve seat insert 74 is clamped between valve body 76 and radial abutment face 75. When valve seat insert 74 is so `secured in position, seal ring 74s disposed in external annular groove 74g in insert 74 cooperates with member 22 to form a fluid tight joint therewith such that fluid entering the valve well 69 from bore or passage 67 can reach ball chamber 73 only by passing through the bore 74B in the valve seat insert 74 and between the valve seat insert 74 and ball 72, when the fluid is under sufllcient pressure to unseat ball 72, the spring 70 being of such size and strength as to impose a predetermined force on ball 72 urging same into fluid tight sealing engagement with valve seat insert 74 in the position illustrated in FIG. 4.

An axial chamber 82 is provided in valve body 76 in direct communication with valve seat insert bore 74b. An axial slideway is provided in valve body 76 extending from chamber 82 to upper end S4 of valve body 76. Slideway 83 is finished to close tolerances by lapping, honing or the like. A slideable Valve member 85 is received in slideway S3 for sliding movement. End 86 of slide valve member 85 advances furtherest into slideway 83. Slide valve member 85 consists of several integral portions extending in series arrangement from end 86 and being successively in order a sealing section 87 the surface of which is adapted to form a substantially fluid tight seal with the cooperating cylindrical wall face of slideway 83, a tapening portion 8S adapted to permit varied metering of hydraulic fluid to effect lowering of the lift as will be hereinafter described, a sealing portion S9 adapted to sealingly cooperate with slideway wall face S3 to preclude movement of hydraulic llulid axially of the slideway past sealing portion 89, a tapered metering portion 9i) having a conically tapered surface which is shifted axially with reference to valve body end face 84 by movement of slideable valve member 85'. Such shifting of portion 90 permits varied metering of the flow of hydraulic fluid to the sump 39 as hereinafter described and a sealing portion 91 adapted to sealingly cooperate with the face of slideway 83 to eect a seal which precludes movement of hydraulic fluid from the mouth of slideway 83 when the slide 85 is advanced axially into valve 76 with at least a portion of sealing portion 91 disposed Within slideway 83, As shown in FIGS. 4, 5, and 6, slideable valve member 85 has a shoulder 92, the radial end face 93 of which is adapted to cooperate with end face S4 of the valve body and thus limit advancement of slideable valve member 85 into slideway 83. Slideable valve member 85 has an axial bore 94 extending from end 86 toward shoulder portion 92. One or more ports 95 provide communication from bore 94 outwardly through the conic surface of portion 90. Bore 94 is counter bored to receive split sleeve member 96, preferably a split tubular form spring member, which, when placed in cooperating relation to slideable valve member 85 Shown in FIGS. 4, 5, and 6 tends to resiliently expand in the counter-bored portion of bore 94. The lower end of split or slotted sleeve member 96 is plugged by the shank portion 97 of abutment 9S.

Referring to FIG. 4, when hydraulic fluid is discharged through bore or passage 67 into valve well 69 it enters an annular gallery-like portion 69a of valve well 69 between valve seat insert 74, the wall of the valve Well, sealing 99s supported by flange 99 of the valve body 76 and the portion of the valve body extending from flange 99 to valve seat insert 74. A plurality of apertures 101 are provided in the valve body, communicating with chamber 82 and the annular gallery-like portion 69a of valve well 69 into which hydraulic fluid may be discharged from bore 67. Thus, when slideable valve member 85 is in a position of axial displacement, such as that in which it is shown in FIG. 4, a portion of the conically tapered surface of portion 90 projects outwardly from end face 84 of valve body 76, hydraulic .fluid may flow from passage 67 and successively through the adjacent portion 69a of valve well 69, apertures 101, chamber 82, slot 162, the interior of member 96, bore 94, aperture or port 95, and the space between the conic surface of slide portion 90 and the slideway defining face 83 adjacent valve body end 84. Since portion 91 is not under such circumstances in scaling engagement with the surface defining slideway 83, the hydraulic fluid may ow through the opening disposed anularly of slide portion 90. Hydraulic fluid flowing from slideway 83 outwardly through end 34 of the valve body 76 at that point reenters the sump charnber 39. Thus, movement of slide valve member S5 in the direction of arrow S in FlG. 4, will increases the area of the opening disposed annularly of the slide member in the plane of valve body end face 84. Movement of the slide member 85 from the position in which it is shown in FIG. 4 and in the direction opposite to that indicated by the arrow S, will etect reduction of the area in the plane of end 84 of the annular opening through which hydraulic fluid may flow to the sump 39 and the area of the annular opening will be reduced to zero when portion 91 commences to enter slideway 83. From the foregoing it may be seen that axial displacement of slideable valve member 85 from the position in which it is shown in FlG. 4 will serve to correspondingly alter the metered llow of hydraulic fluid back to the sump chamber 39 between limits of maximum and zero values. Thus, when slideable valve member 85 is in the position in which slide portion 90 is completely withdrawn from slideway 83 operation of pump 4S will serve to circulate hydraulic liuid from the sump to passage 67 and therefrom through the valve back to the sump, as spring 70 is selected so as to impose a seating force on valve ball 72 as will maintain the valve ball in sealing relation to seat insert 74 and preclude passage of hydraulic liuid between ball 72 and seat insert 74 under pressures present in bore 74B, when all or nearly all of portion 90 is withdrawn from slideway 83. However, when slide valve member 85 is advanced into slideway 83 so as to progressively advance portion 90 thereof into slideway 83, the cross-sectional area of the annular opening in the plane or" face 84 through which hydraulic fluid reenters sump 39 is progressively decreased. Since hydraulic liuid is delivered to annular gallery portion 69a from bore 67 from pump d8 as previously described, the fluid pressure in valve seat insert bore 74B increases as the tlow of hydraulic liuid back to sump 39 is decreased. When the hydraulically applied force acting on valve ball 72 exceeds the opposed forces urging the ball 72 on seat 74, valve 72 is lifted from its seat as illustrated by FIG. 5 and hydraulic huid passes from bore '74B into ball chamber 73. Thus, through axial shifting of valve slide member 85 so as to advance portion 90 thereof progressively into slideway 33 it is possible to increase the ow of hydraulic lluid from bore 74B past ball 72 from zero to maximum tlow and by opposite shifting of the slide member 85 to withdraw portion 90 from slideway 83, the ow can be decreased from any value to zero.

As shown more particularly in FIGS. 3 and l1 the tluid which moves from bore 74B past ball 72 passes successively through ball chamber 73, passage d, litt well 105 or starting bore 105 into cylinder chamber 112.

As shown most clearly in FIG, 3 lift piston rod 107 is secured to piston 103 having suitable sealing means such as seal ring 109. A tang 110 extends from the lower end of piston rod 107 in such manner that it substantially fills lift cylinder well 105 when rod 107 and piston 103 are in the limit position of downward advancement.

Thus when the piston is in the lowered position, only very minute amounts of hydraulic lluid can pass around tang 110 and upwardly through well 105 into the lift cylinder. When the piston rod 107, piston 108 and tang 110 are in the position shown in FIG. 3, hydraulic uid may pass from passage 104 through passage 106 past valve member 111 into the chamber 112 defined by member 22, cylinder 36 and piston 10S. As shown in FG. 13, valve member 111 is a thin square member received in the enlarged portion 106g of the fluid passage. Gasket 37 overlies a portion of the recess 106 and serves to preclude movement of valve member 111 therefrom. As shown in FIG. 3, the depth of portion 106g is greater than the thickness of valve member 111 such that the latter may rise so as to permit lluid to flow from bore 106 around valve member 111 into chamber 112 of the cylinder.

As hydraulic fluid flows through passage 106 around valve 111 into portion 112 of the cylinder, lifting forces are hydraulically applied to the end face of piston 108 annularly of tang 110, and also to the end face of tang 110, so that piston 108 and associated parts will start up in substantially the same way from its lowest position as it does when no portion of tang 110 is in well 105. It may be noted that as soon as the piston 10S has advanced upward a short distance hydraulic lluid enters well more directly and applies lifting force against end face of the tang. As soon as the tang has been completely withdrawn from well 105 the fiow of fluid through well 105 is suiciently free that the companion ilow through passage 106 drops to negligible volume in comparison to the volume flowing into the lift cylinder through well 105.

Fluid may be continuously introduced into portion 112 of the cylinder until the piston 108 has been advanced into engagement with the stop ring 114 seated in an annular -groove provided in spaced relation to the upper end of cylinder 35. Stop ring 114 also serves as a retaining ring upon which piston rod bushing 115 rests. In sequence upwardly from lower piston rod bushing 115, are piston rod bushing spacer 116, upper piston rod bushing 117, piston rod seal 118, piston rod wiper 119, piston rod wiper retainer 120, and upper stop or retaining ring 121. When piston 100 engages stop ring 114, further increase in volume of the hydraulic liuid receiving chamber 112 in cylinder 36 under piston 108, is precluded and hydraulic fluid which would otherwise llow toward and into the cylinder can no longer do so. To relieve any excessive build-up of the hydraulic Huid pressure under such conditions, a relief by-pass to sump 39 is provided as shown in FIG. 9. Passage 62 has an extended portion of reduced diameter 62e which extends to relief valve chamber 122, the remote end of which isiclosed by plug 123. Valve member 124 in chamber 122 is adapted to seat at 125 when a tang portion thereof 126 extends into the adjacent portion of bore 62e. Thus, when the rate of pump delivery of hydraulic fluid exceeds the rate at which such part or the fluid may pass into the portion 112 of the lift cylinder and the remainder may pass back to the sump 39 through the opening annularly of portion 00 of the slide member 05, theI pressure will rise in the passages including 62 to a level at which valve member 124 will be hydraulically advanced toward plug 123 to compress the preloading valve spring 127. When valve member 124 is advanced toward plug 123 a distance such that tang 126 is withdrawn from bore 62e, hydraulic fluid may ow to relief valve chamber 122 and from there in passage 128 into sump 39.

I prefer to provide a shield comprising a top 100 mounted on piston rod 107 between retaining rings 103 and subjacent to tapered portion 107 c provided for mounting a chair, operating table or other structure on rod 107. A skirt 100s is secured to the periphery of top 100 to form an inverted, deep-cup-like lshield for the members housed therein.

To control operation of motor 49 and reciprocation of slideable valve member 85, a pair of pedals are provided. As shown in FIGS. l, 2, 2a and 3, a pair of supports 131 are secured in upstanding relation to chair base 20. Shaft 132 is journalled for angular movement about its axis in supports 131 and secured by suitable means not shown against axial displacement with reference to supports 131. Adjacent each end of shaft 132 is a pedal mounting arm 133 secured in fixed relation to shaft 132 and the pedals 130 are secured to respective mounting arms 133 by respective pivot pins 134 so that the pedals may rock through a predetermined arc about pivot pin 134 and may also rock with shaft 132 about the axis 7 thereof. As shown in FIG. 3 the angle through which pedal 130 may swing with reference to the axis of pivot pin 134 is that angle between the position in which pedal 130 is shown in full lines and the position in which it is shown in dash-double-dot lines denoted by arrow K. Annularly of pedal shaft 132, a biasing compression spring 135 is provided adjacent each support 131 and between each support 131 and the adjacent pedal 130. Between each biasing compression spring 135 and `pedal mounting arm 133, a sliding motion transfer collar 136 is provided. A transfer pin 137 parallel to shaft 132 is supported for sliding movement in `a bore provided in pedal mounting arms 133. Pin 137 is in cooperation with pedal 130 and the adjacent sliding transfer collar 136 such that swinging of pedal 130 through the angle K from the full line position to the double-dot-dash line position, will advance collar 136 toward the nearest support 131, incidentally effecting further compression of biasing spring 135. A short transfer pin 13S, parallel to shaft 132, is supported for sliding movement in a bore provided in support 131 and is biased to move toward sliding collar 136 in a fashion subsequently described herein. Thus, when collar 136 is advanced toward the adjacent support 131, short transfer pin 138 advances a corresponding distance in like direction. In a similar fashion long transfer pin 139 cooperates with its respective collar 136 and is provided with an additional support member 140. As shown in FIGS. 1, 2, 2a and 3, crank arm 141 is secured in xed relation to shaft 132 by pin 142 for rocking in unison therewith. Pivot pin 142 also serves to mount pedal stop bar 143 beneath lever arm 141 and switch actuator arm 144 therebeneath. Biasing spring 149 has a central loop-shape portion cooperatively engaging head portion 145 of pivot pin 142 and cooperates with switch actuator 144 to resiliently bias same toward the position in which it is shown in FIG. 1. It is to be noted that the switch actuator 144 and pedal stop bar 143 are secured together by screws 146 so that they swing in unison. Thus, it can be seen that pins 138 land 139 cooperate with respective upstanding arms 147 and 148 of switch actuator 144 and that the transfer pins are thus resiliently urged toward the respective pedals 134) by the spring 149 which biases the switch actuator `and pedal stop bar as above mentioned. Pedals 130, transfer pins 137 and collars 136 are biased toward positions remote from supports 131 by compression springs 135. As shown in FIG. 2 a switch 150 with actuating arm 151 is mounted on lever 141 in a position in which the arm 151 will cooperate with switch actuator 144 so as to close the switch when the switch actuator 144 and pedal stop bar 143 are swung into subjacent aligned relation to lever arm 141. Switch 150 is the switch controlling current in the electrical circuit supplying current to motor 49 and relay 50. To swing switch actuator 144 and pedal stop 143 through the angle from the motor inoperative position H to the motor operating position E, indicated in FIG. l, the pedal 130 is swung through the angle K, also indicated in FIG. 1. An adjustable abutment 152 is shown in the form of a screw in threaded engagement with chair base beneath the end portion of lever 141 in FIGS. l, 2 and 2a. Abutment 152 is adjustable longitudinally, that is vertically, to establish a predetermined limit on rocking of lever 141 about the axis of shaft 132. When abutment 152 is placed in a desired position, it may be locked in that position by tightening of lock nut 153. The shaft 155 is mounted on lever 141 and supports contact roller 154 in predetermined relation thereto. Roller 154 contacts the upper surface of lever 156, the remote end of which is pivoted, by pin 169, to support 157. A pivot pin 158 couples the lower end of connecting rod 159 to lever 156. The upper end of connecting rod 159 is coupled by pivot pin 160 to lever 161 and contact roller 162. Lever 161 is also pivotally secured by pivot pin 163 to lug 164 of sump head 26. As shown in FIGS. 1 and 3 slide valve member 85 is substantially aligned with valve rod 165 which extends upwardly from portion through a guideway provided in sump head 26, in which is located a seal 166, to its upper end resiliently urged upwardly against contact roller 162 by spring 167 loaded in compression between valve body 76 and slide valve member flange 168. Thus, it may be seen that spring 167 acting on the valve slide and through the valve rod and associated linkages urges lever 156 to swing in a clockwise direction about pivot pin 169 as viewed in FIGS. 2 and 2a. Since roller 154 is urged into continuous contact with the upper surface of lever 156 by gravitational forces acting on pedals 130, lever 141, and pedal stop bar 143, biasing of lever 156 by spring 167, also serves to bias lever 141 and associated parts to rotate in a counterclockwise direction about the axis of pedal shaft 142 as viewed in FIGS. 2 and 2a. The aforementioned biasing of levers 156, 141 and associated members by action of spring 167 are limited by cooperation of valve rod flange 170 with stop boss 171 of sump head 26. The limit position established by boss 171 and valve rod flange 170 corresponds to the position of the valve slide member 85 in which portion thereof is substantially fully withdrawn from slideway 83.

To start motor 49 and resultant pumping of hydraulic iluid in the fashion previously described, pedal is swung laterally through the angle K into the dashdouble-dot line position indicated in FIG. 1 to simultaneously swing pedal stop bar 143 and switch actuator 144 into subjacent alignment with lever 141 to close switch 150. Since the entire hydraulic system, from sump 39 through pump 4S back to sump 39 as well as other portions of the system which may be subjected to hydraulic uid pressure as the result of operation of pump 48 and manipulation of valve slide rod S5, is cornpletely filled with hydraulic iluid and has no air or gas lled expansion chambers or the like, motor 49 reaches normal operating speed and hydraulic pressure rises to operating levels with near instantaneous rapidity, motor 49 being one having a high starting torque. Thereafter, pedal 130 may, as part of a continuation of the switch closing movement, be depressed through such portion of an angle corresponding to angle P indicated in FIG. 2. The limit of downward advancement of pedal 130 is determined by cooperation of pedal stop 172 with abutment 152 when bar 143 is subjacent to and aligned with lever 141 and pedal stop 172 is in the position indicated by double-dot-dash lines in FIG. 2. Such depression of pedal 130 in the double-dot-dash position shown in FIG. 1 and rocking of pedal shaft 132 and associated lever 141 through angle P, shifts the valve actuating linkage to a position in which tapered portion 90 of the valve slide member 85 and an adjacent portion of sealing portion 91 are advanced into slideway 83 into a position coresponding to that illustrated in FIG. 5. This position of maximum advance under motor operating conditions, directs the -full flow of hydraulic lluid from the pump through the system past valve 72 into lift chamber 112 until the piston is raised to a position in which it engages stop member 114 unless the pedal 130 is manpulated so as to terminate operation of the motor or permit sufhcient quantity of t-he hydraulic iluid to return to thc sump 39 to lower lluid pressure in bore 74B to a level such that valve member 72 may reseat. The by-pass shown in FIG. 9, of course serves to divert fluid to the sump 39 in the event the piston 108 is stopped and continuing pump operation produces an associated rise in uid pressure in the system. It may be seen that by appropriately depressing pedal 130 in the double-dot-dash position the flow of hydraulic fluid to the cylinder to raise the piston 108 may be infinitely varied as desired between l zero and full llow. It may be noted as shown in FIG. 5, abutment 98 remains in spaced relation to valve ball 72 when pedal stop 172 is in engagement with abutment 9 152. Thus, valve ball 72 cannot be mechanically held od of its seat by abutment 9S while motor 49 is operating.

To lower the lift, that is to permit piston 16S to advance downwardly in cylinder 36, pedal 130 is swung about the axis of shaft 132 while in the Iposition shown in lfull lines in FIG. 1. When pedal 136 is in the latter position, pedal stop bar 143 and motor switch actuating member 144 are in the position illustrated in full lines in FIG. l, corresponding to the position designated H therein. Under such circumstances the pedal stop 172 and pedal stop bar 143 are neither interposed between lever 141 and abutment 152 nor can stop 172 contact abutment 152. Lever 141 may thus swing from a position such as is shown in full lines in FIG. 2a to the position shown in double-dot-dash lines in that figure, that is may swing through an angle D. Since the angle D through which lever 141 swings under such circumstances is substantially greater than the angle P through which the lever swings when the pedal stop 172 and pedal stop bar 143 are interposed between lever 141 and abutment 152 as shown in FIG. 2, the valve actuating linkage members coupled to lever 156 will advance the valve slide member 85 into slideway 33 to a limit position illustrated in FIG. 6. Since the motor 49 is not operating when pedal 130 is in the full line position as shown in FIG. l, the depression of pedal 130 merely advances the slide member 85 into slideway 83 until abutment 98 makes mechanical contact with valve ball 72 and further advancement of slide member 85 serves to mechanically lift valve ball 72 from its seat 74. When ball 72 is so lifted, hydraulic uid ows from portion 112 of the cylinder through well 1135, ypassage 194, ball chamber 73, into valve seat bore 74B.

As the slide member 85 is advanced to move ball 72 further toward the position shown in FIG. 6, sealing portion 87 of the slide member is advanced from slideway 83 into chamber 82 and as tapered portion 83 is advanced into chamber 82 an annular opening of increasing crosssectional area is provided through which hydraulic iiuid may fiow through slideway 83 and port 175 into an annular gallery-like portion of 176 of the valve well, from which it flows through port 177 to sump 39. Since the depression of pedal 139 in the full line position shown in FIG. 1 controls directly the extent to which tapered portion SS is advanced into chamber 32, the greater the depression of the pedal 130 the more rapid the fiow of hydraulic iiuid back to the sump and thus the more rapidly the piston approaches the limit `position shown in FIG. 3. It should be noted that as piston 108 approaches the limit position shown in FiG. 3 valve member 111 will be seated and preclude flow of hydraulic fluid through passage 106 and tang 11i) moves into cylinder well 195 and limits the rate of flow of fluid from the cylinder to limit the rate of speed at which piston 19S moves i-n the final portion of its approach to the limit position shown in FIG. 3. As will be noted in FIG. 3, well 1135 extends below passage 1154 and the advance end of tang 11@ moves past passage 154 to provide additional hydraulic cushioning which eliminates bumping as piston 108 stops in the limit position shown.

Thus, operation of the lift disclosed herein entails manipulation of either of the pedals 1343 to effect vertical movement. By moving the pedal 130 into the doubledot-dash line position the pump is placed in operation and the degree to which the pedal is depressed determines the rate at which hydraulic fluid is admitted to the cylinder and thus directly controls the rate of ascent of the lift. Similarly, the degree of depression of the pedal 130 in the -full line position shown in FIG. l, directly controls the rate at which hydraulic fluid is permitted to ow from the cylinder and thus directly controls the rate of descent of the lift. It should be noted that the rates of ascent and descent are subject to controlled variation between zero and maximum, at the will of the operator 1@ and precise levels of lift elevation may be obtained irrespective of the direction `from which they are approached.

In the operation of any pump such as 4S sound waves or sound pressure pulsations are produced and tend to travel through uid such as hydraulic uid under substantial pressure. To substantially eliminate noises and related vibrations resulting from operation of pump 4S I have provided an acoustic filter 4comprised of compliance elements 54 and 58 with inertance elements between ittings 55 and 57 and between iitting 59 and valve Well 69. The inertance elements are long passages having a crosssectional area substantially less than the cross-sectional area of the hollow chambers, compliance elements 54 and 58.

The combination of a compliance element and an inertance element forms an acoustic filter of the low-pass type whose action in an hydraulic system is analogous to the action of a low-pass filter made up of inductance and capacitance elements in an electrical circuit. The acoustic filter is such that the frequency of the pulsations t-o be eliminated is well within the attenuation band of the filter. In the embodiment described, the acoustic filter is of the Z-element, 2-section ladder type. Substitution of a single compliance element or a single inertan-ce element for this filter, or any of the various combinations of these elements which form low-pass filters of any desired degree .of complexity, would in effect be the substitution of an element of a much less desirable and much less effective lten It should be noted that the fiuid conducting members extending from pump 48 to valve well 69 are `completely iilled with hydraulic iiuid. In acoustic filters composed of 2-element -sections in ladder type arrangements, the sharpness of the cut off is enhanced by increase in the number of sections in series. However, as the number of sections becomes larger the filtering advantage vcontributed by each additional section is a smaller fraction of the whole and practical limits on the number of sections will exist.

Having thus described what presently appears to be a prefer-red embodiment of the instant invention, it will be apparent to those having ordinary skill in the art to which this invention pertains, that various modifications and changes may be made in the illustrative embodiment without departing from t-he spirit or the scope of the appended claims.

Therefore, what is claimed as new, and is desired to secure by Letters Patent, is:

1. In an electro-hydraulic lift the combination compris- `ing Ian hydraulic sump, an hydraulic Iliquid filled liquid `circulating circuit having a motor driven pump, a compliance element of substantial volume and cross-sectional area, an inertance element of substantial volume and small cross-sectional area, a back flow check valve, a control valve, said sum-p receiving liquid from said control valve for withdrawal by said pump, an extendible lift connected in communication with said circuit through said check valve, and means for actuating said control valve and controlling operation of said motor driven pump during operation of which .pump liquid is continuous-ly Withdrawn from said sump and pumped through said Vcompliance element, inertance element, and control valve, said `control valve being biased to return said liquid to said sump, said control valve actuating means being actuatable to operate said control valve to throttle the fiow of liquid to said sump so as to raise the pressure on the 'liquid approaching the control valve from said pump and thereby cause a quantity of said liquid to ilow through said check valve int-o said extendible lift at such Varied rate as desired between the .limits of Zero ow and full fiow when said motor driven pump is in operation and being actuat-able to operate said check valve to throttle the flow of a quantity of said liquid at such varied rate as desired between the limits of zero flow and full flow from said eXtendible Ilift to said sump while retaining said motor driven pump in inoperative condition to effect retraction of said lift where- 'by said lift may be placed in a precise condition of desired extension approached from either direction.

2. In a human support having an hydraulic lift extension of which is controllable by manipulation of a control valve while electrically driven pump means of said lift is operating and controllably retractable by manipulation of said control valve while said electrically driven pump means is not operating, the combination comprising a rotatable shaft, a pedal, means mounting said pedal on said shaft for rotating said shaft and for swinging through an angle of arc having first and second ends and about an -axis which is in fixed relation to said shaft and extends transversely 4of the shaft axis, valve actuating linkage connecting said shaft and said control Valve, said valve being actuated by swinging of said pedal and shaft about the axis of said shaft, and electric switch means controlling a supply of current to said electrical-ly driven pump means, said sw-itch means being open when said pedal is at the first end of said angle of arc and being held closed by said pedal when same is at the second end of said angle of arc.

3. In a human support having an hydraulic lift extension of which is controllable by manipulation of a control valve while electrically .driven pump means of said lift is operating and controllably retractable by manipulation of said control valve while said electrically driven pump means is not operating, the combination comprising a rotatable shaft, a pedal, means mounting said pedal on said shaft for rotating said shaft and for swinging through an angle of arc having first and second ends and about an axis which is in fixed relation to said shaft and extends transversely of the shaft axis, valve actuating ylinkage connecting said shaft and said control valve, said valve biasing said rotatable shaft to rotate about the shaft axis t-oward a predetermined position and being actuated by swinging of said pedal and shaft about the axis `of said shaft, electric switch means controlling a supply of current to said electrically driven pump means, said switch means being open when said pedal is at the first end of said angle of arc and being held closed by sai-d pedal when same is at the second end of said angle of arc, and means precluding swinging of said pedal from the first end of said angle of arc to the second end of said angle of arc when said shaft is rotated about the shaft axis from the position toward which same is biased.

4. In a human support having an hydraulic lift extension -of which is controllable by manipulation of a control valve while electrically driven pump means of said lift is operating and controllably retractable by manipulation of said control valve while said electrically driven pump means is not operating, the combination comprising a base `for said support, a rotatable shaft mounted thereon, means biasing said shaft to -rotate about its axis to a predetermined rest poistion, a pe-dal, means mounting said pedal on said shaft for rotating said shaft and for swinging through an angle of arc having first and second ends and about an axis which is in fixed relation to said shaft and extends transversely of the shaft axis, valve actuating linkage connecting said shaft and said control valve, said valve being actuated by swinging of said pedal and shaft about the axis of said shaft, electric switch means controlling a supply of current to said electrically driven pump means, said Switch means being open when said pedal is at the first end of said angle of arc and being held closed by said pedal when same is at the second end of said angle of arc, and means precluding swinging of said pedal from the first end of said angle of arc to the second end of said angle of arc when said shaft is not in the rest position.

5. An electro-hydraulic device operable at variable rates determined by liquid supply thereto ranging from zero to full flow comprising in combination an hydraulic sump, an hydraulic liquid filled liquid circulating circuit including an acoustic filter, a control valve intermediate said filter and said sump and an electrically operable pump for pumping hydraulic liquid from said sump through said filter and control valve to said sump, a hydraulic liquid actuable device connected to said circuit between said pump and the discharge to the sump from the control valve, a check valve for checking ow of liquid from the liquid actuatable device to the circulating circuit and means for actuating said control valve to direct a portion of the hydraulic liquid as desired through said check valve to said device to actuate same at a desired rate when said pump is operated and to unseat said check valve to permit liquid to flow as desired from said device to said sump when said pump is not operating.

6. An electro-hydraulic lift operable at variable rates determined by liquid supply thereto from zero to full fiow comprising in combination an hydraulic sump, an hydraulic liquid filled liquid circulating circuit including an acoustic filter, a control valve intermediate said filter and said sump and an electrically operated pump for pumping hydraulic liquid from said sump through said filter and control valve to said sump, an hydraulic lift connected to said hydraulic liquid filled liquid circulating circuit between said pump and said control valve, a check valve between said hydraulic liquid filled liquid circulating circuit and said hydraulic lift for checking liquid flow from said hydraulic lift to said circuit and means for actuating said control valve as desired to direct a portion of the hydraulic liquid past said check valve to said lift to extend same by throttling the flow of hydraulic liquid to said sump while said pump is operated and to permit throttled flow of liquid from said lift to said sump by actuating said control valve to unseat the check valve as desired when said pump is not operating.

7. In an electro-hydraulic lift the combination comprising a hydraulic sump, a hydraulic liquid-filled liquidcirculating circuit having a motor driven pump, a compliance element of substantial volume and cross-sectional area, an inertance element `of substantial volume and small cross-sectional area, a backflow check valve, a control valve, said sump receiving liquid from said control valve for withdrawal by said pump, an extendible lift in communication with said circuit through said check valve, and means for actuating said control valve and controlling operation of said motor-driven pump during operation of which pump liquid is continuously withdrawn from said sump and pumped into said liquid-filled circuit from which it may return to said sump through said control valve, said control valve being biased to return said liquid to said sump while said check valve retains liquid in said extenible lift, said control valve actuating means being actuatable to operate said control valve to throttle the dow of liquid to said sump so as to raise the pressure on the liquid approaching the control valve from said pump and thereby cause a quantity of said liquid to flow through said check valve into and extend said extendible lift when said motor-driven pump is in operation and being actuatable to operate said check valve to throttle the flow of a quantity of said liquid from said extendible lift to said sump while retaining said motor-driven pump in inoperative condition to effect retraction of said lift.

8. In an electro-hydraulic device the combination comprising a hydraulic sump, a hydraulic liquid-filled liquidcirculating circuit having a motor driven pump, a compliance element of substantial volume and cross-sectional area, an inertance element of substantial volume and small cross-sectional area, a check valve and a control valve, said sump receiving liquid from said control valve for withdrawal by said pump, a hydraulically operable device in communication with said cricuit through said check valve, and means for actuating said control valve and controlling operation `of said motor driven pump during which liquid is continuously withdrawn from said sump and pumped through said compliance element, inertance element and control valve, said control valve being biased to return said liquid to said sump, said control valve actuating means being actuatable to operate said control valve to throttle the flow of liquid to said sump so as to raise the pressure on the liquid approaching the control valve from said pump and thereby cause a quantity of said liquid to ow through said check valve into said hydraulically operable device at a rate desired between the limits of zero flow and full ow when said motor driven pump is in operation and being actuable to operate said check valve to throttle the ilow of a quantity of said liquid at a rate desired between the limits of zero ow and full flow from said hydraulically operable device to said sump while retaining said motor driven pump in inoperative condition to effect reverse operation of said device.

9. An electro-hydraulic device operable at speeds in the range lof zero to full speed, said device comprising in combination an hydraulic sump having an outlet and an inlet, a hydraulic liquid lled liquid circulting circuit intermediate said outlet and said inlet, an electrically operable pump for pumping hydraulic liquid from said sump outlet into said circuit, said circuit including a control valve intermediate said pump and the inlet of said sump, a check valve, a hydraulic lift connected through said check valve to said circuit between said pump and the discharge to the sump from the control valve and lever means controlling operation of said pump to start and stop same when said control valve is open and actuating said control valve to direct a portion of the hydraulic liquid as desired to said lift to actuate same at a desired speed when said pump is operated and to reversely operate said lift by controllingly opening said check valve to permit liquid to flow as desired from said lift to said sump when said control valve is open and said pump is not operating.

10. An electro-hydraulic lift operable at speeds in the range of zero to full speed, said lift comprising in combination a hydraulic sump having an outlet and an inlet, a hydraulic liquid filled liquid circulating circuit intermediate said outlet and said inlet, an electrically operable pump for pumping hydraulic liquid from said sump into said circuit, said circuit including a control valve intermediate said iilter and the inlet of said sump, a hydraulic cylinder, a ram reciprocable in said cylinder and defining with said hydraulic cylinder, a hydraulic liquid iilled chamber of variable volume connected through a check valve to said hydraulic liquid iilled liquid circulating circuit between said pump and said control valve and lever means controlling operation of said pump and actuating said control valve as desired to direct a portion of the hydraulic liquid to said cylinder chamber to extend said ram -by throttling the flow of hydraulic liquid to said sump while said pump is operated and to permit liquid to flow from said cylinder chamber to said sump by controllingly actuating said check valve to regulate flow of liquid from said cylinder chamber to said sump when said pump is not operating.

11. In an electro-hydraulic lift having a hydraulic liquid filled circuit, the combination comprising a hydraulic sump having an outlet and an inlet, a liquid filled circuit connected to said sump outlet and said sump inlet and including a motor driven pump, and a control valve, said sump receiving liquid from said control valve for withdrawal by said pump, a cylinder, a ram reciprocable in said cylinder and deiining therewith a liquid filled chamber of variable volume in communication with said liquid lled circuit, a check Valve intermediate said liquid lled circuit and said chamber, lever means controlling operation of said pump and actuating said control valve, operation of said motor driven pump effecting continuous withdrawal of liquid from said sump and continuous pumping of a ow of same into said liquid filled circuit, lever means being actuable to start operation of said pump while said control valve is 1open and while said pump is operating to operate said control valve to so throttle the flow of liquid from said circuit to said sump as to raise the pressure on the liquid flowing between the pump and said control valve and divert a portion of said liquid flow through said check valve into said chamber to increase the volume thereof by moving said ram relative to said cylinder as desired and said check valve being openable by said control valve actuating lever means to throttle the flow of liquid from said chamber to said sump when said pump is not in operation.

References Cited by the Examiner UNITED STATES PATENTS 1,927,752 9/1933 Pardee 103-223 2,170,890 8/1939 Allen 60-51 X 2,253,597 8/ 1941 Wyne 60-52 X 2,311,864 2/ 1943 Parsons. 2,570,241 10/ 1951 Hutchison 230-236 2,727,470 12/ 1955 Ludwig 103-223 3,014,344 12/1961 Arnot 60-52 FOREIGN PATENTS 239,475 12/ 1924 Great Britain.

JULIUS E. WEST, Primary Examiner, 

10. AN ELECTRO-HYDRAULIC LIFT OPERABLE AT SPEEDS IN THE RANGE OF ZERO TO FULL SPEED, SAID LIFT COMPRISING IN COMBINATION A HYDRAULIC SUMP HAVING AN OUTLET AND AN INLET A HYDRAULIC LIQUID FILLED LIQUID CIRCULATING CIRCUIT INTERMEDIATE SAID OUTLET AND SAID INLET, AN ELECTRICALLY OPERABLE PUMP FOR PUMPING HYDRAULIC LIQUID FROM SAID SUMP INTO SAID CIRCUIT, SAID CIRCUIT INCLUDING A CONTROL VALVE INTERMEDIATE SAID FILTER AND THE INLET OF SAID SUMP, A HYDRAULIC CYLINDER, A RAM RECIPROCABLE IN SAID CYLINDER AND DEFINING WITH SAID HYDRAULIC CYLINDER, A HYDRAULIC LIQUID FILLED CHAMBER OF VARIABLE VOLUME CONNECTED THROUGH A CHECK VALVE TO SAID HYDRAULIC LIQUID FILLED LIQUID CIRCULATING CIR- 